In a large bowl, combine oat bran, flour, baking powder, baking soda and salt. In a medium bowl, whisk yogurt, milk, egg and oil to combine. Pour yogurt mixture into oat bran mixture and stir until not quite combined (you should still see lumps of flour). Fold in chocolate chips until just mixed. Let stand 10 minutes. Preheat oven to 200ºF.
Preheat a griddle or large skillet over medium-low heat. Mist with cooking spray (or brush with melted butter) and drop batter by 1/4 cupfuls. Cook until underside is golden (gently lift with a spatula to check), 2 to 3 minutes. Flip pancakes and cook until browned on other side, about 1 minute longer. Keep pancakes warm on a heatproof plate in oven while cooking remaining pancakes. Pass warm maple syrup at the table with pancakes, if desired.